In the formation of imaging and in particular photographic paper it is known that the paper base is resin coated and on the side contacting the image the resin may contain a white pigment such as TiO.sub.2. During the manufacture of the resin coated paper difficulties occur in which the resin is heated to several hundred degrees and pumped through melt processing equipment that has a high level of metal surface area. Difficulties can occur with hot tacky polymer as it flows over these metal surfaces. The polymer tends to stick to these metal parts and can result in lines or other imperfections. These imperfections can result in the loss of significant commercial value or add to the cost to manufacture imaging products.
It has been proposed in U.S. Pat. No. 5,244,861 to utilize biaxially oriented polypropylene sheets laminated to cellulose photographic paper for use as a reflective receiver for the thermal dye transfer imaging process. In the formation of biaxially oriented sheets described in U.S. Pat. No. 5,244,861, a co-extruded layer of polypropylene is cast against a water cooled roller and quenched by either immersion in a water bath or by cooling the melt by circulating chill liquid internal to the chill roll. The sheet is then oriented in the machine direction and in the transverse direction. While a variety of materials may be used to create a biaxially oriented sheet, one of the preferred materials is polypropylene because of its strength and processing properties during the orientation. In addition the cost of this material makes it cost effective to use. One of the problems with polypropylene is that gelatin based coating layers to not adhere to polypropylene polymers as well as to polyethylene polymers. A means to achieve the desired adhesion is to provide a biaxially oriented sheet that has a skin layer of polyethylene. While this helps to resolve the adhesion problem, melt processing problems are encountered during the manufacturing phase of a multi-layer structure. The problem is greatest when the polyethylene is the outer most layer and is in contact with the hot metal surfaces. Polyethylene is relatively tacky in relation to other polymers at the desired processing temperatures and will tend to provide higher frictional resistance against the walls of the extrusion equipment. When this occurs in multi-layer coatings, the drag forces are transmitted into a shear force across the thickness of the polymer layers and can result in melt fracture or slippage within or at the interface of two polymer layers. This creates a defect in the polymer. There remains a need to improve the flow properties of polymer layers in either a mono or multi-layer structure for imaging and in particular photographic applications without encountering adhesion problems between the image layer and the polymer on top of the paper.
In U.S. application Ser. No. 08/862,708 filed May 23, 1997 it has been proposed to use biaxially oriented polyolefin sheets laminated to photographic grade paper as a photographic support for silver halide imaging systems. In U.S. application Ser. No. 08/862,708 filed May 23, 1997 numerous advantages are obtained by the use of the high strength biaxially oriented polyolefin sheets. Advantages such as increased opacity, improved image tear resistance and improved image curl. While all of these photographic improvements are possible with the use of biaxially oriented polyolefin sheets, there is a need to optimize the adhesion of a photographic or image layer to said sheet.